Modern Vespa

Some folks say they're great, some folks say they damage the crankcase.

What's the real deal?

Maybe it comes down to who and how they were installed. just like after market belts that snap to soon

I've heard the belt chews away at the trans cover. If you feel like having the belt fly apart at 60 mph and lock the rear tire then I would try them. To me that is much too risk to take for the small gains achieved. I did however use thm on my Zuma 125 with great success.

I think the belt chewing at the case/oilpan is a Polini/jcosta issue and more so if running larger rollers. Never heard of that issue with the sliders. In fact the 21x17 sliders for the GTS have been hard to come by and people have been running the ones for the GT. Being smaller these can't push the belt out even as far as stock and certainly not enough to rub on the case.

So, why do people run them?
1. They come in many weights allowing you to tune the variator
2. They are harder and last longer
3. They seem to provide a faster response, don't know why

+1 - sliders are just replacements for the stock rollers - they do not change the geometry of the drive system. Jeeeeez where do you guys hear this shit...

For a stock variator in the LX you should be fine using the correct size.

Never heard of any catastrophic damage or other problems from using the correct size correctly installed in a stock variator.

There are some fit issues with Polini variators for the GTS-not using an extra spacer can result in the belt rubbing on the inside of the case. I think using sliders may exacerbate this.

I've been running them in the Polini in my LX, mostly because I was going through rollers too damn quickly. I like-but don't love-the sliders.

I have them in my scoot and like the performance .

The belt will rub against the case IF you put them in the wrong way (easy to do).... at least they do in my scoot, with my belt. I am using Kymco factory parts and OEM belt.

Not saying everyone will have the same experience. I feel they removed the flat spot int he acceleration in the 25-40 MPH range and when coasting that range, the "drifty" feeling I get of the rollers hunting of the right spot is gone. This is most apparent for me when riding in 'slow and go' (not stop and go) traffic and while splitting lanes at these speeds. Basically at these speeds i coast, the gas a little and then coast again. Rollers were slow to accelerate in the middle of the coasting sessions. Sliders remove most of the drifty/coasting sensation and accelerate sooner in these situations.

On a 250 or 300 engine with 21mm sliders, there will be NO transmission case or belt damage. Just make sure that the stock washer is in situ between the gudgeon pin and the outer variator half pulley.

(I think I might have been the originator of the Dr Pulley plus damage story which was erroneous.)

I've now got a total of 9000km on 2 sets of Dr Pulley sliders. They didn't wear out, I was just pissfarting around with different weights. Certainly had no abnormal wear issues. Just make sure to get the right size- the Dr Pulley website is a bit obtuse on this front.

Do some searches here on "stock roller sizes" or somesuch, there has been plenty posted about this. The right weight will be to match stock, or maybe slightly (like half a gram) lighter. You can mix sets evenly (3 of each alternated around the variator) to get precise weights, but be careful- the weight is not marked on the slider itself, only the tin.

Extensive Personal Experience.

Weights being equal in size or weight, one being the traditional round roller the other a slider, the shape of the Dr Pulley slider allows the weight to more further up the variator ramp. That is a fact. Order a set and see for yourself by just a simple install. Because of their design the slider can fit in spaces a round slider cannot.



MRP in Florida used my Zuma as a test bike when the Zuma first came out. I had the bike at their shop and ran it on the dyno using all different clutches, variators and sliders. I saw firsthand how the Dr Pulleys work. I was there all day playing with it and the tech and I did about every combo possible. The Zuma trans cover has tons of free space so belt rubbing simply wasn't a problem no matter what setup was used. We also polished the inside of the case and made it smooth in case the belt rubbed at highway speeds. It did not.

If there is room under the trans case no problem, on a GTS there is not and moving only a little bit more than stock can cause a belt to rub. To be honest I don't want any issues with my 300 because I use the bike mostly for highway and sustained high speed riding. I loved the way the Dr Pulleys worked on my Zuma and would gladly use them on the GTS if they didn't rub.

If you don't believe me and think I'm blowing smoke up your ass and don't have any experience with Dr Pulley here is the youtube video of my bike at MRP. Everything they sell was tried on my bike and I was right there with them working on it. This was years ago before anyone knew of DR Pulley for a GTS
Pics of the damage to a GTS belt and case can be seen on the following thread. I have seen others too and I will continue to look for them. To be honest I don't care if you have a catastrophic belt failure, but I would hate to see anyone get hurt using a product that didn't work well in our bikes. I have NOTHING to gain by showing you this other than to possibly save you headache and "possible" injury.



http://www.gtsownersclub.co.uk/forum/viewtopic.php?f=16&t=2774&hilit=belt+rubbing

When I changed my belt at 15000km, I could still read the text printed on the outside. Only 5000km was with Dr Pulleys, but that included some lengthy freeway jaunts and spirited back country riding. No damage whatsoever.

Cheekythomas at GTSowners does not mention if there was any other issues, if the correct size was used, or if they were incorrectly installed.

My personal experience in a GTS250 is that, with the correct size correctly installed, a weight not dissimilar to stock (not heavier), in a stock variator with a stock belt, there is no problem.

I agree. And that pic on the GTS forum thread showing metal removed from the crankcase is fallacy. That groove is already machined out of the casing by Piaggio. If you do get belt contact in this area, you can add an extra stock washer.

Hmm lets see " the internet"

It's physics - I've several sets of Dr Pulleys and have settled on a good balance for my MP3 500. Love 'em.
Your post is confusing in that first you say you tried all sorts of combos and no belt damage and then you say that you've seen *others* damages. I experimented with spacers in between the pulley (what we call the Fuzzy washer) and got a very minor amount of belt damage from the case - but that was ME changing the geometry of the system. You mention the shape as allowing it to go farther - but that would be with a reduced diameter/radius meaning less opening than the stock round rollers. I maintain that if you have enough oomph to force the Dr Pulleys out far enough to make the pulley strike the case then you can do the same with stock rollers - properly sized the Dr Pulleys match the OD of the stock rollers.

...and my experience is with the LX150, the bike the OP has.

I installed Dr. Pulley sliders in a Polini 6-roller variator 6000 miles back after I kitted my engine. I've ridden the scooter pretty hard since then, including a 4000-mile round trip out west. When I opened up the tranny case a couple of weeks ago to check on things, there was absolutely NO belt damage nor any evidence of rubbing on the case. Most of the sliders showed almost no wear, but one had worn badly and very unevenly, as though it had somehow gotten cocked in the ramp. The variator seemed to be functioning fine, though, and there was no abnormal noise.

I stuck some Polini rollers in the variator temporarily while I waited for replacement sliders to be delivered, but sliders are going back in ASAP. 6000 miles of good service works for me... I'm sold!

Thanks everyone. Now I just need a torque wrench.